Spatial and seasonal heterogeneity of sea ice microbial communities in the first-year ice of Terre Adélie area (Antarctica)

Abstract

Spatial and temporal changes in sea ice microbial communities were investigated at 4 stations located along a south-north transect on the land-fast ice of Dumont d'Urville station area (Adélie Land, 66°40' S, 141°01' E) during the ice coverage period (April to December). A seasonal pattern was observed in microalgae, bacteria and protozoan abundance distribution. A maximum chlorophyll a concentration occurred during fall ice formation in the surface layer with the highest values at the near-shore station (100 to 215 µg l -1 ). A second maximum was observed before ice breaking in the bottom ice (50 to 90 µg l -1 ). Microalgal communities were dominated by diatoms (> 86% of the total cells), mainly represented by Fragilariopsis, Nitzschia, Navicula and Pseudonitzschia species. Fragilariopsis curta was the dominant species during the first bloom whereas Fragilariopsis cylindrus, Nitzschia longissima and Tropidoneis sp. were the main contributors during the second bloom at the bottom ice core. Maximum protozoan abundance was recorded during the fall bloom in the surface layer with dominance of ciliates, which contributed more than 75% of total cell numbers. During this period, the maximum ciliate abundance was associated with the maximum bacteria and diatom numbers and microalgal biomass. The dramatic decrease of the ice algal biomass from south to north paralleled that of the underlying water phytoplankton available for new ice incorporation. The spatial algal biomass decrease could explain the parallel decrease in the abundance of bacteria and heterotrophic ciliates through trophic interactions. KEY WORDS: Antarctica · Land-fast ice · Microbial communities · Chlorophyll a · Nutrients Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 43: [95][96][97][98][99][100][101][102][103][104][105][106] 2006 (Watanabe et , Garrison & Buck 1991, Archer et al. 1996, McMinn 1996, Moro et al. 2000, Riaux-Gobin et al. 2000. However, phytoflagellates are often dominant during spring in the upper sea ice (Stoecker et al. 1997(Stoecker et al. , 1998. Sea ice contains a wide variety of bacterial assemblages. Most bacteria isolated from sea ice have been found to be pigmented and highly coldadapted, with both free-living and epiphytic bacteria present (Grossi et al. 1984). Most taxa isolated from sea ice belong to the γ-proteobacteria and the CytophagaFlavobacterium-Bacteroides division (Bowman et al. 1997, Gozink et al. 1998, Junge et al. 1998, Nichols et al. 1999, Reddy et al. 2002. 16S rDNA clone library analysis corroborated these culture data (Brown & Bowman 2001). Heterotrophic protozoa are also present in sea ice (Garrison & Buck 1991, Stoecker et al. 1993, Song & Wilbert 2002 and are mainly composed of ciliates, nanoflagellates and dinoflagellates (Archer et al. 1996, Garrison et al. 2005). They play a major role in the removal of algal and bacterial biomass in Antarctic waters (Becquevort et al. 2000, Caron et al. 2000, Vaqué et al. 2004. Despite the lack of data on th...

Persistence of bacterial and archaeal communities in sea ice through an Arctic winter

“…, 1977; Delille and Rosiers, 1996; Delille et al. , 1997; Fiala et al. , 2006), not even the extreme conditions of the winter sea ice we studied exerted any more than very limited (statistically undetectable) selective pressure at the taxonomic level on the bacterial and archaeal communities entrapped in this ice.…”

Sea ice diatom contributions to Holocene nutrient utilization in East Antarctica

“…curta and F . cylindrus are not only able to thrive under the ice but also multiply successfully within the ice [ Fiala et al ., ]. As such, F .…”

Chlorophyll‐a in Antarctic Landfast Sea Ice: A First Synthesis of Historical Ice Core Data

“…Historically, studies on Antarctic fast ice algal communities have focused primarily on the taxonomy and physiology of algae inhabiting high‐biomass microhabitats (Arrigo et al, ; Grossi et al, ; McMinn, Pankowskii, et al, ; Stoecker et al, ; Whitaker & Richardson, ). Time series studies have been conducted in specific regions but overall remain sparse (Carnat et al, ; Delille et al, ; Fiala et al, ; Günther & Dieckmann, ; Watanabe et al, ). Here we compiled a comprehensive database of ice algal Chl a concentrations from Antarctic fast‐ice cores collected from different regions around the continent.…”